9. Alternate mechanisms of carbon fixation Flashcards
What are stomas
Plant cells responsible for the exchange of CO2 and O2 and the release of water
How will stomas react if tempture increases in an unchanged plant
If temp increases, to prevent water loss, plants will close stomata to preserve water
What happens to the oxygen and carbon levels of an unchanged plant once the stoma is closed
- Once closing stomata, CO2 can’t go in but photons are still going in producing O2
- Increase O2 level in leaves when stomata closed
- When O2 increased, rubisco doesn’t work well (no sugars or glucose produced)
- Plant will die bc no energy from sugar even though lots of light
Where does the calvin cycle occur in unchanged plants
Everywhere in the plant cell
What is the name for unchanged plants
C3 Plants
What are the two types of cells in C4 Plants
- Mesophyll shell at top of leaf
- Bundle sheath at bottom of leaf
Why is it good for C4 plants to have two types of cells
- To keep O2 level really low, created a mechanism to move calvin cycle into bundle sheath
- CO2 in environment moves into mesophyll cells, change to C4 molecule which donates carbon into calvin cycle
- No O2 inside the bundle sheath
How does the seperation of the calvin cycle in C4 plants prevent plant death
Oxygen can not enter the sheeth where the carbon cycle takes place. Rubisco will not confused CO2 and O2 and every round of the calvin cycle will be effective so the plant gets proper energy.
What tupe of seperation does C4 plants use
Separation by Location
What is the simularity between C3 and C4 plants
Calvin cycle works the same but is in a different area
Where are CAM plants found
Desert Area
When does the Stoma open in CAM plants, and where does the CO2 go
- Open stomata at night to allow CO2 in
- Once CO2 in, instead of going through Calvin cycle, CO2 changes to organic acid
When does the stoma close in CAM plants and why
- During day, stomata close and use light reactions to use CO2 as a source of making glucose
- During day, organic acid releases CO2, allowing CO2 into calvin cycle
Use an analogy to explain how the CAM plants work
- Like putting food in a fridge to eat later
Is there a division of location in CAM plants
No
What type of seperation do CAM plants use
Separation using time
Explain Mesophyll cells
- O2, light reactions
- Loosely arranged around the bundle sheath cells
- Pre calvin cycle reaction occurs in these cells
- CO2 is fixed into a four carbon molecule (malate)
- Four carbon molecules shuttled to bundle-sheath cells
Explain bundle-sheath cells
- No O2, dark reactions
- Tightly packed around the veins in the leaf
- Only matale can go in bundle sheath (made for C4 cycle)
- The calvin cycle can only occur in these cells
- 100% per cycle for greeting G3P
- Rubisco has high efficiency
What does CAM plants stand for
- CAM stands for crassulacean acid metabolism
- Named after the plant family it was first discovered which is succulents
What happens in CAM plants during the night
- Stomata open
- CO2 enters leaves and is fixed into organic molecules (malate/malic acid)
- Malate stored in mesophyll cells in vacuoles
What happens in CAM plants during the day
- Stoma close
- Prevent water loss
- Light dependent reactions supply ATP and NADPH for Calvin cycle
- CO2 released from malate which is incorporated into carbohydrate production calvin cycle
- Carbohydrate production during day
- Oxaloacetate available in cells
What are the 4 factors that affect photosynthesis
- Llight
- Carbon dioxide
- Tempeture
- Oxygen concentration
How does light affect photosynthesis
- Rate of photosynthesis increases as light intensity increase until all pigments been used - saturation point
- Light and CO2 are limiting factors
How does carbon dioxide affect photosynthesis
- Rate of photosynthesis will increase until the plants overwhelmed by high levels of CO2
- As light increases, CO2 uptake increases
- More light you have, more CO2 you need
How does tempeture affcet photosynthesis
- Many temperature-dependent enzymes work in this process and therefore demand strict temperature limits to operate at peak efficiency
- Temp to high OR too low, enzymes responsible for everything will denature
How does oxygen concntration affect photosynthesis
- Increase CO2 in plants, O2 is going to complete for rubisco
